WPF - Handle case where Bitmap in InteropBitmapInfo is null

[jamespearce2006]

The OnPaint call arrives on a thread other than the UI thread. This means it is possible that the InvokeRenderAsync method, which is dispatched back to the UI thread, will get called after the Dispose method. In this case, a NullReferenceException is thrown, because FileMappingHandle is no longer set.

[amaitland]

Prefer to eval == first, flows better when reading code.

[amaitland]

CreateBitmap() is usually called after the bitmap has already been cleared. In the scenario your trying to handle hear is it possible for bitmap != null?

Ideally would fail fast, have a code block like this as the first operation.

// Unable to create bitmap without valid File Handle (Most likely control is being disposed)
if (FileMappingHandle == IntPtr.Zero)
{
  return null;
}

[jamespearce2006]

I think my update fulfils your request. Let me know.

On 5 May 2015 at 22:54, Alex Maitland notifications@github.com wrote:

In CefSharp.Wpf/Rendering/InteropBitmapInfo.cs
#1003 (comment):

     }

     public override BitmapSource CreateBitmap()
     {
         var stride = Width * BytesPerPixel;

•        Bitmap = (InteropBitmap)Imaging.CreateBitmapSourceFromMemorySection(FileMappingHandle, Width, Height, PixelFormat, stride, 0);
  

•        if (FileMappingHandle == IntPtr.Zero)
  

•        {
  

•            ClearBitmap();
  

CreateBitmap() is usually called after the bitmap has already been
cleared. In the scenario your trying to handle hear is it possible for bitmap
!= null?

Ideally would fail fast, have a code block like this as the first
operation.

// Unable to create bitmap without valid File Handle (Most likely control is being disposed)if (FileMappingHandle == IntPtr.Zero)
{
return null;
}

—
Reply to this email directly or view it on GitHub
https://github.com/cefsharp/CefSharp/pull/1003/files#r29717350.

[amaitland]

Close 😄 I'll remove the else (redundant) and move the stride calculation after the if when it's eventually time to merge this 👍

[amaitland]

Applied a similar change to WritableBitmapInfo see 561507b